The present invention relates to a semiconductor luminance or light source device, being built by disposing a plural number of light emitting diodes on a heat or thermal diffusion plate. Specifically, the present invention relates to a cooling structure of such the semiconductor light source device.
In recent years, since the light emitting diodes, as one of the semiconductor elements, are able to emit therefrom the lights of the three primary colors, such as, red (R), green (G) and blue (B), for example, and therefore, they attract attentions of being applied to be a color display, for example, and also to be a light source device, enabling to emit a white color light from those light components of red (R), green (G) and blue (B). Further, in the following Patent Document 1, there is already known a semiconductor LED assembly, which mounts a large number of chips of the light emitting diodes, as being semiconductor elements, on a sub-mount thereof, to be shared with.
However, the light emitting diode (LED), as being semiconductor element, has high heat-dependency. Thus, the LED has a characteristic of lowering efficiency of converting from electric power into lights, when increasing temperature thereof. For this reason, as was known from the following Patent Document 2, for example, a technology was already proposed and also studied, of cooling down such the LED, being high in the heat dependency, with applying a Peltier element, i.e., a semiconductor thermoelectric cooling element, therein.
Patent Document 1: Japanese Patent Laying-Open No. 2003-008083 (2003); and
Patent Document 2: Japanese Patent Laying-Open No. 2004-342557 (2004).
By the way, normally, control is made on a brightness level of the light emitting diode (LED) through controlling the ON/OFF timing thereof; i.e., pulse (short pulse) operation (or driving) is adopted, in general. For this reason, for such the LED element, it is also necessary to make the cooling thereon, responding to the said drive pulse.
However, in particular, within the cooling structures for the LED chip building up a lightening unit, with applying the Peltier element therein, as is disclosed in the Patent Document 2 mentioned above, the said Peltier element is disposed, to be sandwiched or put between an upper substrate, on which the LEDs are mounted, and a lower substrate, in the structures thereof. However, in the structures disclosed therein, a light source array connecting a large number of LED chips in series and a Peltier module connecting also a large number of Peltier elements in series are connected in series, electrically, and for this reason there brings about a drawback that it is large in the time constant thereof.
For such the reason, in particular, with the cooling structures for the LED chips, which is disclosed in the Patent Document 2, a problem is pointed out that it is not necessarily sufficient to be the cooling structure, in particular, for cooling the LED elements, which are driven with the short pulses, effectively. Also, within the light source device mounting the large number of LED chips and the Peltier elements therein, it is demanded to reduce the number of the parts much more, and to reduce the cost thereof, as well.